Header extension to retain core cover and maintain constant compression on outer fins

ABSTRACT

A heat exchanger and, in particular, a heat exchanger for a motor-vehicle air-conditioning system includes a manifold with apertures for heat exchanging tubes and projections at the ends of the manifold for retaining members. The projections are designed to maintain the position of the retaining members during manufacture of the heat exchanger so that defects are not introduced into the heat exchanger during production.

BACKGROUND OF THE INVENTION

The present invention relates to a heat exchanger and, in particular, toa heat exchanger for a motor-vehicle air-conditioning system.

In a parallel flow condenser, poor compression of condenser componentsleads to several cosmetic defects during brazing of condensercomponents. These defects lead to scrap or additional handling andrework and can even lead to customer dissatisfaction and productrejection. Poor compression can result due to natural variation in thefin and tube height, which can be very difficult to control.Additionally, thermal expansion in a braze furnace can cause compressionjoints to expand and lose their effectiveness.

Defects caused by incomplete compression include:

(1) Fin Drop—incomplete compression will not retain the fin enough toovercome gravity as the condenser is processed, causing the fin to fallout of position. Fin Drop occurs when the fin drops out of positionbetween two tubes.

(2) Fin Up—incomplete compression will not retain the fin enough toovercome the force of blowers that blow upward to remove excess fluxduring processing and/or furnace barriers (“curtains”) that drag alongthe top face of the condenser as it passes from one furnace zone to thenext. The fin is lifted upward as a result. The cosmetic effect of thisdefect is similar to fin drop, but the fin is out of position in theopposite direction.

(3) Fin Window—incomplete compression will not retain the fin in placesuch that the gap between the manifold and fin is unchanged as it passesthrough the furnace. Fin Window can occur when the fin's end is caughton curtains in the furnace and compressed back. When the fin windowoccurs in the corner of the core, it is usually due to this cause.

In addition to the three defects mentioned above, Core Cover Shift isanother defect which can occur. In Core Cover Shift, the outer corecovers shift during installation of the braze frames, causing anundesirable cosmetic defect, though condenser performance is unaffected.This typically occurs when the cover is hung up on the compression framethat holds the condenser throughout the brazing process. Products havingthis defect cannot be reworked and can only be scrapped. Core CoverShift occurs when the cover slides along the fin. Note that the cover isnot centered in the manifold and exposes the fin below.

Fin Drop and Fin Up are typical failure modes for certain types ofcondensers. Incomplete compression can occur, as stated before, due tonatural variation in the fin and tube height in the corebuild process.Where the corebuild process can be controlled to minimum levels,incomplete compression can still result as a natural effect of thermalexpansion in the furnace.

In order to combat the effect of thermal expansion in the furnace (whichcannot be avoided), the core can be protected by putting a rod or a barunderneath and along the fins most typically affected. This bar canserve as a preventive barrier that prevents fins from dropping even whenloss of compression would otherwise cause the fin to drop. This bar,however, is ineffective against fin up.

There are, however, several disadvantages to the bar placed under thecorner fins. Specifically: (a) if the core is not completely seated, thebar is ineffective; (b) if the bar is bent or deformed, it can damagethe fin it was supposed to protect; and (c) if the bar is not treatedproperly, the fin it supports can braze to the bar, causing the fin tobe damaged.

In order to combat the effect of the curtains pulling the fin up or backto cause Fin Up or Fin Window, a protective “cage” can be placed on topof the condenser prior to brazing. This cage, which is basically alattice of stainless wire made to mount to the compression frame abovethe condenser, without touching the condenser, protects the core fromthe furnace curtains but allows sufficient airflow to make a good brazeas well as being light such that it does not become a heat sink. Thissystem, however, will not prevent Fin Up caused by flux blowers.

Unfortunately, the cage has a principle disadvantage in that it addslabor to the process in a non-value added manner. It is also subject tobeing damaged, making it difficult to install in place and creating arisk for a furnace wreck.

In order to prevent core cover shift, the effect of the covers gettinghung up on the compression frame should be prevented. Keeping the framesclean and maintained helps but is not a perfect fix for this effect.Additionally, although workers can be encouraged to review a productjust after the frame is installed before passing the condenser on in theprocess, if a condenser is found to be incompletely seated in the frame,a mallet can be used to return it to the correct position; however, thisapproach is undesirable.

The major disadvantage to controlling the corebuild and finmill toensure consistent compression and tube and fin height is that it isdifficult or impossible to do so in a “preventative” manner. Typically,problems are discovered after the fact; even if the affected condenserscould be found, there is a good chance that they have already begun thebraze process, after which they are unrecoverable. Unfortunately, even100% inspection of the condenser is only minimally effective.

Keeping the frames consistently clean to prevent core cover shift is alabor-intensive process and difficult to control in that there is notgood certainty that all the frames are being cleaned in the correctperiodicity. Additionally, frame cleanliness is limited in itseffectiveness toward preventing core cover shift. The practice of usinga mallet to seat a condenser is undesirable for reasons made obvioussimply by observation of the process.

An apparatus for retaining end members in place is described in DE 19814 827. This apparatus includes a side plate that is fixed to themanifold by members. However, this design does not allow condensation orother fluid to flow between the side plates and the manifold. Therefore,condensation that develops at the side plate may collect and lead tocorrosion of the heat exchanger.

Another apparatus for retaining end members in place is described inU.S. Pat. No. 5,894,885. This apparatus includes end tubes that arefixed to collectors. This design imparts added cost and does not allowfor condensation or other fluid to flow between the collectors and theend tubes. Therefore, condensation that develops at the junction betweenthe collectors and the end tubes may collect and lead to corrosion ofthe heat exchanger.

SUMMARY OF THE INVENTION

Accordingly, one object of the present invention is to overcome orcompensate for the effects of natural variation of fin and tube heightand thermal expansion of the furnace, while restraining the outer corecovers that serve as a protection for the outer fins.

According to one embodiment of the present invention, a header for aheat exchanger includes a manifold, wherein the manifold includes aplurality of apertures for tubes, and wherein each end of the manifoldincludes a plurality of projections for retaining an end member.

According to another embodiment of the present invention, a heatexchanger includes a first manifold, a second manifold orientedsubstantially parallel to the first manifold, a plurality of tubesextending between the first and second manifolds, and at least one endmember disposed adjacent to the plurality of tubes and extending betweenan end of the first manifold and an end of the second manifold, whereineach end of the manifold includes a plurality of projections forretaining the end member.

According to another embodiment of the present invention, an automotiveheating and cooling system includes devices for providing hot fluid andcold fluid and a heat exchanger, which includes a first manifold, asecond manifold oriented substantially parallel to the first manifold, aplurality of tubes extending between the first and second manifolds, andan end member disposed adjacent to the plurality of tubes and extendingbetween an end of the first manifold and an end of the second manifold,wherein each end of the manifold includes a plurality of projections forretaining the end member.

According to still another embodiment of the present invention, a motorvehicle includes a motor vehicle and a heat exchanger, which includes afirst manifold, a second manifold oriented substantially parallel to thefirst manifold, a plurality of tubes extending between the first andsecond manifolds, and an end member disposed adjacent to the pluralityof tubes and extending between an end of the first manifold and an endof the second manifold, wherein each end of the manifold includes aplurality of projections for retaining an end member.

Further objects, features and advantages of the present invention willbecome apparent from the detailed description of preferred embodimentsthat follows when considered together with the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

An exemplary embodiment of the invention is described in more detailbelow and is represented in the drawings, in which:

FIG. 1 depicts a typical setup of a frame and condenser prebraze.

FIG. 2A and FIG. 2B depict a typical corner joint before and afterbraze.

FIG. 3 is a side view of a representation of outer tube retention,according to an embodiment of the present invention.

FIG. 4 is a top view of a manifold according to one embodiment of thepresent invention.

FIG. 5 is an enlarged view of area B in FIG. 4, showing manifoldapertures for a heat exchanger tubes, according to one embodiment of thepresent invention.

FIG. 6 is an enlarged view of area C in FIG. 4, showing an end of amanifold, according to one embodiment of the present invention.

FIG. 7A is an enlarged view of area D in FIG. 6, showing a projectionfor retaining an end member, according to one embodiment of the presentinvention.

FIG. 7B is an exemplary alternative structure to the structure depictedin FIG. 7A according to another embodiment of the present invention.

FIG. 7C is an exemplary alternative structure to the structure depictedin FIG. 7A according to another embodiment of the present invention.

FIG. 7D is an exemplary alternative structure to the structure depictedin FIG. 7A according to another embodiment of the present invention.

FIG. 8 is a view of an end of a manifold according to one embodiment ofthe present invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

In order to avoid the defects discussed above, the outer core covers areretained so that shifting is impossible, and so that compression loss isminimized in the process. In existing designs, there was no retention ofthe outer fin and core cover during fabrication except for that whichwas created by the compression frame.

In this regard, FIG. 1 shows a typical setup of a frame 300 andcondenser 200 before brazing. The condenser 200 includes a manifold 230at each end and a tube-fin matrix 240 between each manifold 230. Thetube-fin matrix 240 includes heat exchanging tubes 250 and areas 260between tubes 250 for fins (not shown). The compression points 210 areshown for effect only. Typically, compression is along the length of thecover, but compression may end at about 50 mm from the manifolds.

FIG. 2 shows a closer view of a corner joint 220 of the frame 300 andcondenser 200 of FIG. 1. When the condenser 200 and frame 300 are placedin a brazing furnace, the frame components heat up and undergo thermalexpansion. The direction of thermal expansion is indicated in FIG. 2 byarrow X. Thermal expansion is a function of material, the change intemperature, and the length of the material expanding. Long componentsare the ones most affected by thermal expansion. In the case of thecomponents of FIGS. 1 and 2, the core cover is farthest from the centerof the manifold. Also, when the condenser manifold 230 is constructed ofaluminum and the frame 300 is constructed of stainless steel, thethermal expansion of the aluminum condenser manifolds 230 is higher thanthat of the stainless steel frames 300. Thus, as the manifold 230 growsin the furnace, the outer core cover 270 is bent against the braze frame300. The first live tube 255, however, is captured by the manifold 230and is a little closer to the center of the manifold. The outer corecover 270, with no retention, is pushed away from the end of themanifold 230. Furthermore, the resulting gap between the outermost livetube 255 and the core cover 270 is made wider than the height of the fin(not shown), and the fin loses its compression.

FIG. 3 is a side view of a representation of outer tube retentionaccording to one preferred embodiment of the present invention. In theexample of FIG. 3, a condenser setup 100 includes a manifold 110, heatexchanging tubes 120 that form areas 130 for fins (not shown), and anouter core cover or member 140. The condenser setup 100 is compressed bya brazing frame 300. According to one preferred embodiment of thepresent invention, manifold 10 includes projections 30 for retaining theouter core cover or member 140 in place during manufacture, includingbrazing. Therefore, because the outer core cover or member 140 ismaintained in position, the first live tube 125 is also held inposition, and the manufacturing defects described above are minimized.

FIG. 4 shows a top view of a manifold 10 according to a preferredembodiment of the present invention. The manifold 10 includes apertures20 for heat exchanging tubes arranged along the longitudinal axis A ofthe manifold 10. The manifold 10 also includes “fingers” or projections30 at each end 40 of the manifold for retaining members 140 at the endsof the manifold. The members 140 retained by the projections may be endplates, unused tubes, or other end members known in the heat exchangingart. The projections 30 may be integral with the body of the manifold10.

FIG. 5 shows a detailed a view of area B in FIG. 4, showing apertures 20for heat exchanging tubes, according to one embodiment of the presentinvention. As shown in the example of FIG. 5, the apertures 20 for heatexchanging tubes may be curved so that the apertures 20 follow thecurvature of the heat exchanging tubes 120. This design promotes joiningof the manifold 10 and heat exchanging tubes 120 during brazing andfurther promotes sealing of the manifold 10 to the heat exchanging tubes120.

FIG. 6 shows a detailed view of an end of the manifold tube 40,according to one embodiment of the present invention. The end of themanifold 40 includes “fingers” or projections 30 for retaining memberswith the manifold. The “fingers” or projections 30 form areas 35 forretaining members 140. These areas 35 may be formed with tightertolerances than the apertures 20 for heat exchanging tubes 120 so thatthe members 140 are firmly held in position during manufacture of thecondenser. Furthermore, the ends of the manifold tubes 40 may include aportion 50 that allows fluid, such as, for example, condensation, toflow between the members 140 and the manifold tube 10. In the example ofFIG. 6, the portion 50 is a flat portion that provides a clearancebetween the member 140 and the manifold 10. The portion 50 may also be anotch in the manifold tube 10 or any other configuration that provides aclearance between the member 140 and the manifold 10.

By providing a portion or clearance between the member and the manifold,fluid, such as, for example, condensation, that collects at the manifoldand member is allowed to flow instead of collecting at the juncture ofthe manifold and the member. This prevents or retards corrosion withinthe manifold. While the portion 50 has been depicted by way of examplehere as a flat portion, the portion 50 may also be formed by one or moreflat or curved surfaces or a combination of flat or curved surfacesprovided that the surface or surfaces provide sufficient clearance topermit fluid to flow between the manifold and the member.

FIGS. 7A, 7B, 7C, and 7D show detailed views of exemplary “fingers” orprojections 30 for retaining a member at the end of a manifold 10,according to further preferred embodiments of the present invention. Inthese further preferred embodiments, the “finger” or projection 30creates a grip area 39 for retaining the member 140 in the manifold. Inthe exemplary configurations depicted in FIG. 7A, FIG. 7B, FIG. 7C, andFIG. 7D, one or more surfaces 37 have been provided which form aclearance between a member 140 (not depicted here for the sake ofclarity) and the manifold 10 (not depicted in its entirety here for thesake of clarity). While the surface 37 has been depicted by way ofexample here as a flat surface, the surface may also be formed by one ormore flat or curved surfaces or a combination of flat or curved surfacesprovided that the surface or surfaces provide sufficient clearance topermit fluid to flow between the manifold and the member. Also, the oneor more sections 37 may be provided in addition to or instead of theportion 50 discussed above.

FIG. 8 shows an end view of a manifold 10, according to anotherpreferred embodiment of the present invention. In the example of FIG.11, the manifold 10 includes projections 30 for retaining a member 140.The projections 30 form a slot or slots that the member 140 is fittedinto so that the member 140 is held in position during manufacture. Themanifold 10 also includes apertures for receiving heat exchanger tubes.In the example of FIG. 8, the first live tube 125 is shown in positionwith the manifold 10.

In the example of FIG. 8, the manifold 10 is shown as a single-piecetube. However, the manifold 10 may also be formed from two or morepieces that form the manifold 10.

Because of the retention of the outer tube using “fingers” 30 integratedin the manifold 10, the outer core cover or member 140 is not pushedaway by the manifold 10 during expansion. Thus the dominant factor indetermining the separation distance due to thermal expansion is nolonger the length of the manifold 10 but rather the distance betweentubes 120. As a result, the effective separation distance affecting theouter fin is greatly reduced, and the fin never loses compression in thebraze cycle. FIG. 3 shows a representation of this effective distance160.

Advantages of the invention include its demonstrated ability throughtrials to eliminate the two largest failure modes currently observedduring condenser production: tube shift and fin drop. Fin Window and FinUp have also been demonstrated to decrease dramatically because of thechange. These improvements are realized with only a nominal increase intooling and piece price.

Another advantage is that this change can be implemented into existingtooling very easily with no noticeable increase in startup scrap. Afurther advantage is that the present invention allows condensation thatmay collect at the end of the manifold to flow out of the manifoldbetween the manifold and the retained member. As a result, prematurecorrosion of the condenser may be avoided.

The foregoing description of preferred embodiments of the invention hasbeen presented for purposes of illustration and description only. It isnot intended to be exhaustive or to limit the invention to the preciseform disclosed, and modifications and variations are possible and/orwould be apparent in light of the above teachings or may be acquiredfrom practice of the invention. The embodiments were chosen anddescribed in order to explain the principles of the invention and itspractical application to enable one skilled in the art to utilize theinvention in various embodiments and with various modifications as aresuited to the particular use contemplated. It is intended that the scopeof the invention be defined by the claims appended hereto and that theclaims encompass all embodiments of the invention, including thedisclosed embodiments and their equivalents.

1. A header for a heat exchanger, comprising: a manifold; wherein themanifold includes a plurality of apertures for tubes; wherein each endof the manifold includes a plurality of projections for retaining an endmember.
 2. The header of claim 1, wherein the plurality of projectionsat each end of the manifold form an opening in the end of the manifold.3. The header of claim 2, wherein the projections form an at leastapproximately semicircular opening at each end of the manifold.
 4. Theheader of claim 1, wherein at least one end of the manifold includes atleast one portion that, in cooperation with the end member, allows fluidto flow between the manifold and the end member.
 5. The header of claim4, wherein the at least one portion comprises a flat portion that doesnot follow the curvature of the end member.
 6. The header of claim 5,wherein the at least one portion comprises a plurality of flat portionsthat do not follow the curvature of the end member.
 7. The header ofclaim 4, wherein the at least one portion comprises at least one curvedsurface.
 8. The header of claim 7, wherein the at least one portioncomprises a combination of curved and flat surfaces.
 9. The header ofclaim 4, wherein the at least one portion comprises a notch in anopening in the end of the manifold.
 10. A heat exchanger, comprising: afirst manifold; a second manifold oriented substantially parallel to thefirst manifold; a plurality of tubes extending between the first andsecond manifolds; and an end member disposed adjacent to the pluralityof tubes and extending between an end of the first manifold and an endof the second manifold, wherein at least one end of the manifoldincludes a plurality of projections for retaining an end member.
 11. Theheat exchanger of claim 10, wherein the plurality of projections at eachend of the manifold form an opening in the end of the manifold.
 12. Theheat exchanger of claim 11, wherein the projections form an at leastapproximately semicircular opening at each end of the manifold.
 13. Theheat exchanger of claim 10, wherein at least one end of the manifoldincludes at least one portion that allows condensation to flow betweenthe manifold and the end member.
 14. The heat exchanger of claim 13,wherein the at least one portion comprises a flat portion that does notfollow the curvature of the end member.
 15. The heat exchanger of claim14, wherein the at least one portion comprises a notch in an opening inthe end of the manifold.
 16. The heat exchanger of claim 13, wherein theat least one portion comprises at least one curved surface.
 17. The heatexchanger of claim 16, wherein the at least one portion comprises acombination of curved and flat surfaces.
 18. The heat exchanger of claim13, wherein the at least one portion comprises a notch in an opening inthe end of the manifold.
 19. An automotive heating and cooling system,comprising: devices for providing hot fluid and cold fluid; a heatexchanger, which includes: a first manifold; a second manifold orientedsubstantially parallel to the first manifold; a plurality of tubesextending between the first and second manifolds; and an end memberdisposed adjacent to the plurality of tubes and extending between an endof the first manifold and an end of the second manifold, wherein atleast one end of the manifold includes a plurality of projections forretaining an end member.
 20. The automotive heating and cooling systemof claim 19, wherein the plurality of projections at each end of themanifold form an opening in the end of the manifold.
 21. The automotiveheating and cooling system of claim 20, wherein the projections form anat least approximately semicircular opening at each end of the manifold.22. The automotive heating and cooling system of claim 19, wherein atleast one end of the manifold includes at least one portion that allowscondensation to flow between the manifold and the end member.
 23. Theautomotive heating and cooling system of claim 22, wherein the at leastone portion comprises a flat portion that does not follow the curvatureof the end member.
 24. The automotive heating and cooling system ofclaim 23, wherein the at least one portion comprises a notch in anopening in the end of the manifold.
 25. The automotive heating andcooling system of claim 22, wherein the at least one portion comprisesat least one curved surface.
 26. The automotive heating and coolingsystem of claim 25, wherein the at least one portion comprises acombination of curved and flat surfaces.
 27. The automotive heating andcooling system of claim 22, wherein the at least one portion comprises anotch in an opening in the end of the manifold.
 28. A motor vehicle,comprising: a motor vehicle; and a heat exchanger, which includes: afirst manifold; a second manifold oriented substantially parallel to thefirst manifold; a plurality of tubes extending between the first andsecond manifolds; and an end member disposed adjacent to the pluralityof tubes and extending between an end of the first manifold and an endof the second manifold, wherein at least one end of the manifoldincludes a plurality of projections for retaining an end member.
 29. Themotor vehicle of claim 28, wherein the plurality of projections at eachend of the manifold form an opening in the end of the manifold.
 30. Themotor vehicle of claim 29, wherein the projections form an at leastapproximately semicircular opening at each end of the manifold.
 31. Themotor vehicle of claim 28, wherein at least one end of the manifoldincludes at least one portion that allows condensation to flow betweenthe manifold and the end member.
 32. The motor vehicle of claim 31,wherein the at least one portion comprises a flat portion that does notfollow the curvature of the end member.
 33. The motor vehicle of claim32, wherein the at least one portion comprises a notch in an opening inthe end of the manifold.
 34. The motor vehicle of claim 28, wherein theat least one portion comprises at least one curved surface.
 35. Themotor vehicle of claim 34, wherein the at least one portion comprises acombination of curved and flat surfaces.
 36. The motor vehicle of claim28, wherein the at least one portion comprises a notch in an opening inthe end of the manifold.